Surface wettability is an important property of solid surfaces. A surface is said to be wettable if a liquid spreads over the surface evenly without the formation of droplets. Such surfaces tend to be hydrophilic in nature, allowing water to spread out. This implies that the forces associated with the interaction of water with the surface are greater than the cohesive forces associated with bulk liquid water. In contrast, water forms droplets on hydrophobic surfaces, implying that the cohesive forces associated with bulk water are greater than the forces associated with the interaction of water with the surface.
Paints and coatings, while protecting the substrate from the environment, can themselves be contaminated by unwanted substances over time. Dirt, for example, can dull the coating by increasing light scattering or by modifying the color component of the coating. Dirt can also affect the durability. It can often be expensive to clean a coated substrate. The chemicals used to clean a coated substrate can make their way into the environment where they can potentially cause great damage. A hydrophilic surface allows water to spread out in a thin layer, thus sweeping dirt off the surface as the water thins out and trickles away. Thus, it is desirable to have a coating with a hydrophilic surface that prevents dirt from sticking to the surface, is self-cleaning, and is made of eco-friendly chemicals.